1. Field of the invention
The present invention relates to an optical information recording/reproducing apparatus for recording, reproducing and erasing optical information by using light reflected from an optical information recording medium such as an optical disk.
2. Description of the Related Art
A general apparatus for recording and reproducing optical information is shown in e.g., Japanese Patent Application Laying Open (KOKAI) No. 64-55745. In such an optical information recording/reproducing apparatus, it is possible to cope with a compact disk and a disk of an additional writing type, but it is impossible to cope with a magnetooptic disk of a rewriting type. Further, no magnetooptic signal can be detected since a diffraction element has no function for polarizing and separating light.
In another general apparatus for recording and reproducing optical information, it is impossible to simultaneously detect a magnetooptic single in addition to a focusing error signal and a tracking error signal, and the optical information recording/reproducing apparatus cannot be made compact and these signals cannot be stably detected at any time.
Further, the general optical information recording/reproducing apparatus cannot be cheaply manufactured, and no electric signal can be stably detected at any time irrespective of a change with the passage of time.
Further, in general optical information recording/reproducing apparatus, it is impossible to increase tolerance in assembly of an optical system and adjustment thereof and the construction of the optical information recording/reproducing apparatus cannot be simplified.
Further, in the general optical information recording/reproducing apparatus, no magnetooptic signal can be detected with high sensitivity.